Sure! if you either never send a packet to any part of the internet which needs a reply, or never connect to the internet at all, you can route to where ever ELSE you like without worry.
For 6you to get any IP packets FROM anywhere on the internet, you have to have a return address same as the US mail.
we used UUCP to send Mail into the internet without any direct connection to the net, it was all serial to the Mail service, and only IP from there.
AOL customers use propritary protocols to Virginia, then become IP at AOL headquarters I love everyone til they prove otherwise, sadly some prove otherwise SO quickly